Magnetic tachometer.



J. K. STEWART.

MAGHTIC TAGHOYETER.

Pulau iss FILED Nov. 1s, was.

Patented Apr. 26, 1910.

20 'index finger being caused by lthe magnetic "-'AUNITED STATES PATENTorales.

i Y JOHN x. STEWART, or omesso, ILLINOIS.

Y MAGNETIC TAcHoMErrin.

To all whom it may concern:

Be it known that I, JOHN K. STEWART, a citizen of the United States,residing at, Chicago, in the county of Cook and State fi of Illinois,have invented new and useful Improvements in Magnetic Tachometers, ofwhich the' following is a specification, reference beingr had to thedrawings forming a part thereof. f Y This invention relates to theVclass of speed-measuring devicesv in which there are associated -threeelements, a magnet, its armature and-a third element of low magneticresistance interposed in the magnetic I' ld, one of the three elementsbeing rotated, and a second having an indicating device, as an indexfinger, and being mounted for oscillation aganst a yieldingT resist-'ance or biasing means, the deflection of the drag of the rotatingelement upon the oscillating element.

It consists in the features of construction and their'. combinationshown and described as indicated in the claims.

In the drawings :-F igure l is a face View of a tachometer embodyingthis invention, the dial plate and armature disk bein; r each in partbroken away to disclose their ele- U ments.' Fig. 2' is an' axialsection of the v ,Y ed the dia-l plate. 13, which is preferablyprotected by a glass, C. At the center of 0 the case', rigid with the.yback `or bottom disk, 1. thereof, there is `erected, preferably formedintegrally with rthe case, a post, 2. This post.Y is reduced in diameterat Aits upper part, forming an inclined shoulder. 3, which 5constitutesv the ball seat of' a ball bearing, -indicated by the balls,D, and about the reduced [Ent there is journaled the magnet' element. Asillustrated, the magnetelemerit, E, comprises a central iron or steel 0member, EL, unmagnetized, which termi- .nates at the lower end in aninterior bevelgear rim, 4, is axially apertured to pass onto the reduceduppergportion of the post.

l and rabbetecl atv both ends et 5 aroundfsaid 5 axial aperture, 6., toafford angular ball seats for the anti-friction balls, D', at theSpecication of Letters Patent.

Applicationled Norember 16, 1908. Serial No. 462,755.

' Patented Apr.V 26, 1910.

upper and lower ends. A take-up cone, 7, is screwed onto the upper endof the post to retain the balls in place, and the entire magnet element.on the post. This central HU member, E1, is secured by drive tit in anaxial apertura? in a second member, E", of non-magnetic material, asbrass, copper or aluminum, and to this second member there are securedthe horse shoe magnets, E3, any convenient number of such magnets beingprovided, four being employed in the structure shown. The non-magneticmember, Ei is recessed to form seats for receiving the magnets E3, whichfit tight in their seats, being, however, additionally secured by bolts,9, for whose Vheads the bolt; holes through themagnet arecylindricallycountei-sunk at 10, so that there shall be no pzotrusion beyond thesurface of the magnet blocks. These bolts take into the member, E2." Themagnets, E, are all disposed with their poles at the upper endalternating 1n circumferential order about the axis of the magnetelement, so that they constitute a multipolar magnet.

The post., 2, is axially bored at 1l from its upper end, and receives atthe bottom of said bore. a step bearing, 12, for the spindle, 13, of adisk, F, of material having low magnet-ic -resistance, as aluminum',which is positioned so as to be spaced a very short, distance from theupper poles of the magnet. The case, ,is interiorly rabbetcd to form ashoulder, 15, for an armature disk, G, which also serves to complete theinclosure of the .hamber in which the magnet and the disk, are located.The spindle, 13, of the disk, beside its step bearinn at 12 may beprovided with a second steadying bearing at 16. at the center of thedisk, G, which is penetrated by the spindle, and carries atits upper endan index finger, H. A little above. the armature disk, G, there islocated a helical spring, J, connected at itsinnerendwithl the spindleand at its outer end lwith a stud," 17, mounted in the armature disk, G.The bottom, 1, of theease has an obliquely projection' hollow boss, 1S,into which' is screwed t. e journal bearing, 19, 01",.2, shaft, 105' K,having ball-bearings. at 2G; `2(l;,-'in said e journahbearing element.This. shaft, K, at

its inner-endwithin the case terminates in l' bevel pinion,` 22, whichmeshes with the internal bmi' geant, for rotating the magnet 110 felement. The shift, K, is designed to be' connected in any convenientmanner with l connection. A

squared and vapertured at the end, 21', to indicate the intention andadaptation for such mounted/on Athe under side oi the armature disk,`G;and the collar, 26, on the spindle,

13, which constitutes the means of securing the inner end of the helicalspring, J, to the spindle, is adjusted about the spindle to cause thesaid helical spring to hold the pin, 23, against said spring stop, 211,with slight, pressure,-that is, so that it may be Withdrawn therefrom byslight magnetic drag upon the disk F `when the magnet is rotated inthedireetion for ceiling the helical spring. The index finger, H, issecured on the spindle to register 1.rith the zero point of the dial, B,when the pin, 23, is against the spring stop, 24.

The `method and principle of operation i of this instrument will beobvious to those familiarwith magnetic tachoineter devices in commonusc. llhen the shaft, K. is rotated and rotates the magnet element, thelines of 'force from (he magnetic poles to' the armature., being cut bythe disk, I", produce a drag upon the disk tending to Y rotate. it inthe saine direction as the magnet,

and such tendency being resisted by the spring, J, results in a partialrotation of the disk, l", causing a deiiection of the index lingeraround the dial proportionate to the speed of rotation of the magnet,the. tension of the spring being adjusted so that a predeterminedinaxin'nnn,speed of rolation of the magnet will producitlic maxiin, 23,projects from the mum delict-.tion for which the dial is giadni ated.The amount of force involved in the drag' upon the disk, F, whichproduces the great, and the instrument. is sensitive to an)` extraneousdisturbance. )my considerable which the disk, li. is contained, or hereble to disturb the accuracy of the indication. f which anl set throughthe lower side of the non-magnetic element. l'1= .impinging against isrotated is constructed. as `shown. with the Fi r this re:

'on the magnetic element which A bearing, 12, deeply thereinl there isobtained wide s read of the bearings of the spindle, 13, w ichcontributes materially to the steadiness of the act-ion of the disk, F,and certainty of the speed indication which it Y gives; indeed, theconstruction shown in this respect very nearly dispenses with thenecessity fortiie bearing, 1G, and reduces to n n almost. negligibleamount the service of this bearing, for the long stemmed oscillatingelement Vstel-,pcd so far below the level of the oscillating disk tendsto balance on that step bearing after the ymanner of a spinning top,andlateral ircssure occurs at the bearing, 16, only so ar as the enti-reinstrument may be subject to jars or disturbance of position.

Preferably the step bearing. l2, for the spindle, 13,being a jewel isembedded iii the upper end of a threaded post or stein, 25, which isscrewed dou-'n through the iixed post, 2, that post being-for thatpurpose axially bored through its entire length, and threaded for a.suitable distance to engage the threaded post, a jam-nut, Q6. being.rprovided on the lower end of the threaded stem or post., :25, to securethe latter against accidental rotation. This construction provides meansfor vertically adjusting the step hearing, 12, to adjust the distance ofthe osi-illating low-resistance element, 1f', from the,

magnet oles for any purpose for which such adiustinent may at any timebe desirable. Y

be adjusted axially, being moved toward oscillation and speed indicationis not very tho. armature. (i, for increasing the action linger, andbeing moved away from the armaagnation of the air within the chamber inture 'for diminishing such action and indiration. Such adjustment of themagnets is such agitation might atleet the. disk, is liarii'ected bymeans of adjusting screws. QT,

be reached for slightly slacking them it'l necessari when the magnet isto ,be thus adjusted. VThe entire case, A, is preti-:ably inclosed in aremovable brass or other -ihin i'inished metal sheath, which closes the;hotes,

iis"

2S and :29, when they are provided foftba purpose stated.

I claim 1. In a magnetic tacliomefrr. ri er tion with a caseyan armaturedisk mounted p on the casel wall and inelosing a chamber within thecase, a post within the caso coaxial with said chamber, a magnet carriermounted-:for rotation on the. post, a vearrieractuating shaft, journaledinthe case wall and projecting into the chamber, for rotating thecarrier; a low resistance disk positioned between the armature disk andone end of the carrier and mounted for osciliation about the axis ofrotation of the carrier,

such carrier being provided with a plurality of peripheral recesses, andhorse shoe magnets mounted in such 'recesses having all their polestoward the disks.

2. 1n a magnetic tachometer in combination with a case, a post withinthe ease. a permanent magnet element and au armature, one mounted forrotation on the post and the other supported fxedly on the case, and alow resistance disk positioned between the magnet and the armature.mounted for oscil lation about the axis of the rotating element; `themagnet elementy eomprlsmg a magneti rarrierof non-magnetic material,

and a -plnrality of horse shoe magnets .se-

Vcured on such earrier arranged in a circle about said axis of rotation,the carrier beincg peripherally recessed to reeelve the magnets, thelatter havlng their outer surfaces substantialiy ilushwith the outersurface of the carrier. Y

- 3. In a magnetic tachometer in combination witha ease. an armaturedisk mounted on thedisk wall and inclosing a chamber within the caf-ze,a post within the case coaxial with .sa-id chamber, a magnet carriermounted for rotationl on the post, a earrieraetuatiupr shaft journaledin the case wall and projectingintolhe chamber, for rotat ing thecarrier; a low resistance disk positioned between the armature disk `andone f end of the carrier and mounted for oscillation about the axis ofrotation ot the carrier, said magnet, carrier comprising, a centralmember by which it is mounted on the post; a non-magnetic member mountedon andencompassing said central member and having a :plurality ofperipheral recesses and horse shoe magnets secured fixedly in suchrecesses Y with their poles faeingjoward said' disks.

4. In a magnetic taehonieter, in combination with a case, a rigid post.withinthe case; a permanent magnctelement and an amature, one mountedfor rotation on the post and the other supported tixedly on the i case;a low-resistance disk positioned between the magnet and the armaturehaving' a spindle provided with a step 4l aringgj within the post andextending through the fixed element; a spring which operates to hold thedisk i-'ieldinglyV against. rotation from a predetermined position;anindieaior earried b v thespindle. and means for adjusting the magnetaxialiv with respect to the distance of its poles from the armature.

In a magnet-ic taehometer. in combination with a ease, a rigid postwithin the case; a permanent, magnet element and :xa armature, oneymounted for rotation on the post and the other supported fixedly on thecase; a .low-resistance disk positioned be.- tween the magnet and thearmature having a spindle provided with a step bearing with in Vthe postand extending through the fixed element; a spring which operates to holdthe disk yieldingly against rotation from a predetermined position; anindicator carried bv the spindle, the magnet. element comprisini; a.plurality of horseshoe magnets and a' carrier on which they are rigidlymounted, and

means for adjusting the magnets longitudi- 3 -nally on the carrier tovaryy the distance from their poles to the armature.

6. In a maf'netic taehometer, in combination with a, case, a rigid postwithin the case; a permanent magnet element and an armature, one mountedfor rotation on the postand the other supported ixedly on the case; alow-resistance disk positioned be tween the magnet. and the armaturehaving; a spindle provided with a .step bearing with in the post andextending through the fixed element; a spring which operates to hold thedisk yieldingly against. rotation from a redetermined position; anindicator carrie by the spindle; the magnet comprising a plurality ofhorseshoe magnets; a non-magnetic i carrier having seats for thehorseshoe magnets; .screws set. through said'carrier iu.- pinging`againstthe neck or bow of the horseshoe magnets respectively, theease'having an aperture through which such screws are accessible. r e

In testimony whereof, I have hereunto set my hand, in the presence oftwo witnesses, at Chicago, Iliinois,'this 12th day of November, 1905.

JOHN K. STEiVART. In the presence of- J Um S. Aorr, M. Garraum: ADY.

